net/netfilter/nfnetlink_acct.c - linux - Git at Google

 /*
  * (C) 2011 Pablo Neira Ayuso <pablo@netfilter.org>
  * (C) 2011 Intra2net AG <http://www.intra2net.com>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation (or any later at your option).
  */
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/skbuff.h>
 #include <linux/atomic.h>
 #include <linux/netlink.h>
 #include <linux/rculist.h>
 #include <linux/slab.h>
 #include <linux/types.h>
 #include <linux/errno.h>
 #include <net/netlink.h>
 #include <net/sock.h>

 #include <linux/netfilter.h>
 #include <linux/netfilter/nfnetlink.h>
 #include <linux/netfilter/nfnetlink_acct.h>

 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
 MODULE_DESCRIPTION("nfacct: Extended Netfilter accounting infrastructure");

 static LIST_HEAD(nfnl_acct_list);

 struct nf_acct {
 	atomic64_t		pkts;
 	atomic64_t		bytes;
 	struct list_head	head;
 	atomic_t		refcnt;
 	char			name[NFACCT_NAME_MAX];
 	struct rcu_head		rcu_head;
 };

 static int
 nfnl_acct_new(struct sock *nfnl, struct sk_buff *skb,
 	     const struct nlmsghdr *nlh, const struct nlattr * const tb[])
 {
 	struct nf_acct *nfacct, *matching = NULL;
 	char *acct_name;

 	if (!tb[NFACCT_NAME])
 		return -EINVAL;

 	acct_name = nla_data(tb[NFACCT_NAME]);
 	if (strlen(acct_name) == 0)
 		return -EINVAL;

 	list_for_each_entry(nfacct, &nfnl_acct_list, head) {
 		if (strncmp(nfacct->name, acct_name, NFACCT_NAME_MAX) != 0)
 			continue;

                 if (nlh->nlmsg_flags & NLM_F_EXCL)
 			return -EEXIST;

 		matching = nfacct;
 		break;
         }

 	if (matching) {
 		if (nlh->nlmsg_flags & NLM_F_REPLACE) {
 			/* reset counters if you request a replacement. */
 			atomic64_set(&matching->pkts, 0);
 			atomic64_set(&matching->bytes, 0);
 			return 0;
 		}
 		return -EBUSY;
 	}

 	nfacct = kzalloc(sizeof(struct nf_acct), GFP_KERNEL);
 	if (nfacct == NULL)
 		return -ENOMEM;

 	strncpy(nfacct->name, nla_data(tb[NFACCT_NAME]), NFACCT_NAME_MAX);

 	if (tb[NFACCT_BYTES]) {
 		atomic64_set(&nfacct->bytes,
 			     be64_to_cpu(nla_get_be64(tb[NFACCT_BYTES])));
 	}
 	if (tb[NFACCT_PKTS]) {
 		atomic64_set(&nfacct->pkts,
 			     be64_to_cpu(nla_get_be64(tb[NFACCT_PKTS])));
 	}
 	atomic_set(&nfacct->refcnt, 1);
 	list_add_tail_rcu(&nfacct->head, &nfnl_acct_list);
 	return 0;
 }

 static int
 nfnl_acct_fill_info(struct sk_buff *skb, u32 portid, u32 seq, u32 type,
 		   int event, struct nf_acct *acct)
 {
 	struct nlmsghdr *nlh;
 	struct nfgenmsg *nfmsg;
 	unsigned int flags = portid ? NLM_F_MULTI : 0;
 	u64 pkts, bytes;

 	event |= NFNL_SUBSYS_ACCT << 8;
 	nlh = nlmsg_put(skb, portid, seq, event, sizeof(*nfmsg), flags);
 	if (nlh == NULL)
 		goto nlmsg_failure;

 	nfmsg = nlmsg_data(nlh);
 	nfmsg->nfgen_family = AF_UNSPEC;
 	nfmsg->version = NFNETLINK_V0;
 	nfmsg->res_id = 0;

 	if (nla_put_string(skb, NFACCT_NAME, acct->name))
 		goto nla_put_failure;

 	if (type == NFNL_MSG_ACCT_GET_CTRZERO) {
 		pkts = atomic64_xchg(&acct->pkts, 0);
 		bytes = atomic64_xchg(&acct->bytes, 0);
 	} else {
 		pkts = atomic64_read(&acct->pkts);
 		bytes = atomic64_read(&acct->bytes);
 	}
 	if (nla_put_be64(skb, NFACCT_PKTS, cpu_to_be64(pkts)) ||
 	    nla_put_be64(skb, NFACCT_BYTES, cpu_to_be64(bytes)) ||
 	    nla_put_be32(skb, NFACCT_USE, htonl(atomic_read(&acct->refcnt))))
 		goto nla_put_failure;

 	nlmsg_end(skb, nlh);
 	return skb->len;

 nlmsg_failure:
 nla_put_failure:
 	nlmsg_cancel(skb, nlh);
 	return -1;
 }

 static int
 nfnl_acct_dump(struct sk_buff *skb, struct netlink_callback *cb)
 {
 	struct nf_acct *cur, *last;

 	if (cb->args[2])
 		return 0;

 	last = (struct nf_acct *)cb->args[1];
 	if (cb->args[1])
 		cb->args[1] = 0;

 	rcu_read_lock();
 	list_for_each_entry_rcu(cur, &nfnl_acct_list, head) {
 		if (last) {
 			if (cur != last)
 				continue;

 			last = NULL;
 		}
 		if (nfnl_acct_fill_info(skb, NETLINK_CB(cb->skb).portid,
 				       cb->nlh->nlmsg_seq,
 				       NFNL_MSG_TYPE(cb->nlh->nlmsg_type),
 				       NFNL_MSG_ACCT_NEW, cur) < 0) {
 			cb->args[1] = (unsigned long)cur;
 			break;
 		}
 	}
 	if (!cb->args[1])
 		cb->args[2] = 1;
 	rcu_read_unlock();
 	return skb->len;
 }

 static int
 nfnl_acct_get(struct sock *nfnl, struct sk_buff *skb,
 	     const struct nlmsghdr *nlh, const struct nlattr * const tb[])
 {
 	int ret = -ENOENT;
 	struct nf_acct *cur;
 	char *acct_name;

 	if (nlh->nlmsg_flags & NLM_F_DUMP) {
 		struct netlink_dump_control c = {
 			.dump = nfnl_acct_dump,
 		};
 		return netlink_dump_start(nfnl, skb, nlh, &c);
 	}

 	if (!tb[NFACCT_NAME])
 		return -EINVAL;
 	acct_name = nla_data(tb[NFACCT_NAME]);

 	list_for_each_entry(cur, &nfnl_acct_list, head) {
 		struct sk_buff *skb2;

 		if (strncmp(cur->name, acct_name, NFACCT_NAME_MAX)!= 0)
 			continue;

 		skb2 = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
 		if (skb2 == NULL) {
 			ret = -ENOMEM;
 			break;
 		}

 		ret = nfnl_acct_fill_info(skb2, NETLINK_CB(skb).portid,
 					 nlh->nlmsg_seq,
 					 NFNL_MSG_TYPE(nlh->nlmsg_type),
 					 NFNL_MSG_ACCT_NEW, cur);
 		if (ret <= 0) {
 			kfree_skb(skb2);
 			break;
 		}
 		ret = netlink_unicast(nfnl, skb2, NETLINK_CB(skb).portid,
 					MSG_DONTWAIT);
 		if (ret > 0)
 			ret = 0;

 		/* this avoids a loop in nfnetlink. */
 		return ret == -EAGAIN ? -ENOBUFS : ret;
 	}
 	return ret;
 }

 /* try to delete object, fail if it is still in use. */
 static int nfnl_acct_try_del(struct nf_acct *cur)
 {
 	int ret = 0;

 	/* we want to avoid races with nfnl_acct_find_get. */
 	if (atomic_dec_and_test(&cur->refcnt)) {
 		/* We are protected by nfnl mutex. */
 		list_del_rcu(&cur->head);
 		kfree_rcu(cur, rcu_head);
 	} else {
 		/* still in use, restore reference counter. */
 		atomic_inc(&cur->refcnt);
 		ret = -EBUSY;
 	}
 	return ret;
 }

 static int
 nfnl_acct_del(struct sock *nfnl, struct sk_buff *skb,
 	     const struct nlmsghdr *nlh, const struct nlattr * const tb[])
 {
 	char *acct_name;
 	struct nf_acct *cur;
 	int ret = -ENOENT;

 	if (!tb[NFACCT_NAME]) {
 		list_for_each_entry(cur, &nfnl_acct_list, head)
 			nfnl_acct_try_del(cur);

 		return 0;
 	}
 	acct_name = nla_data(tb[NFACCT_NAME]);

 	list_for_each_entry(cur, &nfnl_acct_list, head) {
 		if (strncmp(cur->name, acct_name, NFACCT_NAME_MAX) != 0)
 			continue;

 		ret = nfnl_acct_try_del(cur);
 		if (ret < 0)
 			return ret;

 		break;
 	}
 	return ret;
 }

 static const struct nla_policy nfnl_acct_policy[NFACCT_MAX+1] = {
 	[NFACCT_NAME] = { .type = NLA_NUL_STRING, .len = NFACCT_NAME_MAX-1 },
 	[NFACCT_BYTES] = { .type = NLA_U64 },
 	[NFACCT_PKTS] = { .type = NLA_U64 },
 };

 static const struct nfnl_callback nfnl_acct_cb[NFNL_MSG_ACCT_MAX] = {
 	[NFNL_MSG_ACCT_NEW]		= { .call = nfnl_acct_new,
 					    .attr_count = NFACCT_MAX,
 					    .policy = nfnl_acct_policy },
 	[NFNL_MSG_ACCT_GET] 		= { .call = nfnl_acct_get,
 					    .attr_count = NFACCT_MAX,
 					    .policy = nfnl_acct_policy },
 	[NFNL_MSG_ACCT_GET_CTRZERO] 	= { .call = nfnl_acct_get,
 					    .attr_count = NFACCT_MAX,
 					    .policy = nfnl_acct_policy },
 	[NFNL_MSG_ACCT_DEL]		= { .call = nfnl_acct_del,
 					    .attr_count = NFACCT_MAX,
 					    .policy = nfnl_acct_policy },
 };

 static const struct nfnetlink_subsystem nfnl_acct_subsys = {
 	.name				= "acct",
 	.subsys_id			= NFNL_SUBSYS_ACCT,
 	.cb_count			= NFNL_MSG_ACCT_MAX,
 	.cb				= nfnl_acct_cb,
 };

 MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_ACCT);

 struct nf_acct *nfnl_acct_find_get(const char *acct_name)
 {
 	struct nf_acct *cur, *acct = NULL;

 	rcu_read_lock();
 	list_for_each_entry_rcu(cur, &nfnl_acct_list, head) {
 		if (strncmp(cur->name, acct_name, NFACCT_NAME_MAX)!= 0)
 			continue;

 		if (!try_module_get(THIS_MODULE))
 			goto err;

 		if (!atomic_inc_not_zero(&cur->refcnt)) {
 			module_put(THIS_MODULE);
 			goto err;
 		}

 		acct = cur;
 		break;
 	}
 err:
 	rcu_read_unlock();
 	return acct;
 }
 EXPORT_SYMBOL_GPL(nfnl_acct_find_get);

 void nfnl_acct_put(struct nf_acct *acct)
 {
 	atomic_dec(&acct->refcnt);
 	module_put(THIS_MODULE);
 }
 EXPORT_SYMBOL_GPL(nfnl_acct_put);

 void nfnl_acct_update(const struct sk_buff *skb, struct nf_acct *nfacct)
 {
 	atomic64_inc(&nfacct->pkts);
 	atomic64_add(skb->len, &nfacct->bytes);
 }
 EXPORT_SYMBOL_GPL(nfnl_acct_update);

 static int __init nfnl_acct_init(void)
 {
 	int ret;

 	pr_info("nfnl_acct: registering with nfnetlink.\n");
 	ret = nfnetlink_subsys_register(&nfnl_acct_subsys);
 	if (ret < 0) {
 		pr_err("nfnl_acct_init: cannot register with nfnetlink.\n");
 		goto err_out;
 	}
 	return 0;
 err_out:
 	return ret;
 }

 static void __exit nfnl_acct_exit(void)
 {
 	struct nf_acct *cur, *tmp;

 	pr_info("nfnl_acct: unregistering from nfnetlink.\n");
 	nfnetlink_subsys_unregister(&nfnl_acct_subsys);

 	list_for_each_entry_safe(cur, tmp, &nfnl_acct_list, head) {
 		list_del_rcu(&cur->head);
 		/* We are sure that our objects have no clients at this point,
 		 * it's safe to release them all without checking refcnt. */
 		kfree_rcu(cur, rcu_head);
 	}
 }

 module_init(nfnl_acct_init);
 module_exit(nfnl_acct_exit);
	/*
	* (C) 2011 Pablo Neira Ayuso <pablo@netfilter.org>
	* (C) 2011 Intra2net AG <http://www.intra2net.com>
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation (or any later at your option).
	*/
	#include <linux/init.h>
	#include <linux/module.h>
	#include <linux/kernel.h>
	#include <linux/skbuff.h>
	#include <linux/atomic.h>
	#include <linux/netlink.h>
	#include <linux/rculist.h>
	#include <linux/slab.h>
	#include <linux/types.h>
	#include <linux/errno.h>
	#include <net/netlink.h>
	#include <net/sock.h>

	#include <linux/netfilter.h>
	#include <linux/netfilter/nfnetlink.h>
	#include <linux/netfilter/nfnetlink_acct.h>

	MODULE_LICENSE("GPL");
	MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
	MODULE_DESCRIPTION("nfacct: Extended Netfilter accounting infrastructure");

	static LIST_HEAD(nfnl_acct_list);

	struct nf_acct {
	atomic64_t pkts;
	atomic64_t bytes;
	struct list_head head;
	atomic_t refcnt;
	char name[NFACCT_NAME_MAX];
	struct rcu_head rcu_head;
	};

	static int
	nfnl_acct_new(struct sock nfnl, struct sk_buff skb,
	const struct nlmsghdr nlh, const struct nlattr const tb[])
	{
	struct nf_acct nfacct, matching = NULL;
	char *acct_name;

	if (!tb[NFACCT_NAME])
	return -EINVAL;

	acct_name = nla_data(tb[NFACCT_NAME]);
	if (strlen(acct_name) == 0)
	return -EINVAL;

	list_for_each_entry(nfacct, &nfnl_acct_list, head) {
	if (strncmp(nfacct->name, acct_name, NFACCT_NAME_MAX) != 0)
	continue;

	if (nlh->nlmsg_flags & NLM_F_EXCL)
	return -EEXIST;

	matching = nfacct;
	break;
	}

	if (matching) {
	if (nlh->nlmsg_flags & NLM_F_REPLACE) {
	/* reset counters if you request a replacement. */
	atomic64_set(&matching->pkts, 0);
	atomic64_set(&matching->bytes, 0);
	return 0;
	}
	return -EBUSY;
	}

	nfacct = kzalloc(sizeof(struct nf_acct), GFP_KERNEL);
	if (nfacct == NULL)
	return -ENOMEM;

	strncpy(nfacct->name, nla_data(tb[NFACCT_NAME]), NFACCT_NAME_MAX);

	if (tb[NFACCT_BYTES]) {
	atomic64_set(&nfacct->bytes,
	be64_to_cpu(nla_get_be64(tb[NFACCT_BYTES])));
	}
	if (tb[NFACCT_PKTS]) {
	atomic64_set(&nfacct->pkts,
	be64_to_cpu(nla_get_be64(tb[NFACCT_PKTS])));
	}
	atomic_set(&nfacct->refcnt, 1);
	list_add_tail_rcu(&nfacct->head, &nfnl_acct_list);
	return 0;
	}

	static int
	nfnl_acct_fill_info(struct sk_buff *skb, u32 portid, u32 seq, u32 type,
	int event, struct nf_acct *acct)
	{
	struct nlmsghdr *nlh;
	struct nfgenmsg *nfmsg;
	unsigned int flags = portid ? NLM_F_MULTI : 0;
	u64 pkts, bytes;

	event \|= NFNL_SUBSYS_ACCT << 8;
	nlh = nlmsg_put(skb, portid, seq, event, sizeof(*nfmsg), flags);
	if (nlh == NULL)
	goto nlmsg_failure;

	nfmsg = nlmsg_data(nlh);
	nfmsg->nfgen_family = AF_UNSPEC;
	nfmsg->version = NFNETLINK_V0;
	nfmsg->res_id = 0;

	if (nla_put_string(skb, NFACCT_NAME, acct->name))
	goto nla_put_failure;

	if (type == NFNL_MSG_ACCT_GET_CTRZERO) {
	pkts = atomic64_xchg(&acct->pkts, 0);
	bytes = atomic64_xchg(&acct->bytes, 0);
	} else {
	pkts = atomic64_read(&acct->pkts);
	bytes = atomic64_read(&acct->bytes);
	}
	if (nla_put_be64(skb, NFACCT_PKTS, cpu_to_be64(pkts)) \|\|
	nla_put_be64(skb, NFACCT_BYTES, cpu_to_be64(bytes)) \|\|
	nla_put_be32(skb, NFACCT_USE, htonl(atomic_read(&acct->refcnt))))
	goto nla_put_failure;

	nlmsg_end(skb, nlh);
	return skb->len;

	nlmsg_failure:
	nla_put_failure:
	nlmsg_cancel(skb, nlh);
	return -1;
	}

	static int
	nfnl_acct_dump(struct sk_buff skb, struct netlink_callback cb)
	{
	struct nf_acct cur, last;

	if (cb->args[2])
	return 0;

	last = (struct nf_acct *)cb->args[1];
	if (cb->args[1])
	cb->args[1] = 0;

	rcu_read_lock();
	list_for_each_entry_rcu(cur, &nfnl_acct_list, head) {
	if (last) {
	if (cur != last)
	continue;

	last = NULL;
	}
	if (nfnl_acct_fill_info(skb, NETLINK_CB(cb->skb).portid,
	cb->nlh->nlmsg_seq,
	NFNL_MSG_TYPE(cb->nlh->nlmsg_type),
	NFNL_MSG_ACCT_NEW, cur) < 0) {
	cb->args[1] = (unsigned long)cur;
	break;
	}
	}
	if (!cb->args[1])
	cb->args[2] = 1;
	rcu_read_unlock();
	return skb->len;
	}

	static int
	nfnl_acct_get(struct sock nfnl, struct sk_buff skb,
	const struct nlmsghdr nlh, const struct nlattr const tb[])
	{
	int ret = -ENOENT;
	struct nf_acct *cur;
	char *acct_name;

	if (nlh->nlmsg_flags & NLM_F_DUMP) {
	struct netlink_dump_control c = {
	.dump = nfnl_acct_dump,
	};
	return netlink_dump_start(nfnl, skb, nlh, &c);
	}

	if (!tb[NFACCT_NAME])
	return -EINVAL;
	acct_name = nla_data(tb[NFACCT_NAME]);

	list_for_each_entry(cur, &nfnl_acct_list, head) {
	struct sk_buff *skb2;

	if (strncmp(cur->name, acct_name, NFACCT_NAME_MAX)!= 0)
	continue;

	skb2 = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
	if (skb2 == NULL) {
	ret = -ENOMEM;
	break;
	}

	ret = nfnl_acct_fill_info(skb2, NETLINK_CB(skb).portid,
	nlh->nlmsg_seq,
	NFNL_MSG_TYPE(nlh->nlmsg_type),
	NFNL_MSG_ACCT_NEW, cur);
	if (ret <= 0) {
	kfree_skb(skb2);
	break;
	}
	ret = netlink_unicast(nfnl, skb2, NETLINK_CB(skb).portid,
	MSG_DONTWAIT);
	if (ret > 0)
	ret = 0;

	/* this avoids a loop in nfnetlink. */
	return ret == -EAGAIN ? -ENOBUFS : ret;
	}
	return ret;
	}

	/* try to delete object, fail if it is still in use. */
	static int nfnl_acct_try_del(struct nf_acct *cur)
	{
	int ret = 0;

	/* we want to avoid races with nfnl_acct_find_get. */
	if (atomic_dec_and_test(&cur->refcnt)) {
	/* We are protected by nfnl mutex. */
	list_del_rcu(&cur->head);
	kfree_rcu(cur, rcu_head);
	} else {
	/* still in use, restore reference counter. */
	atomic_inc(&cur->refcnt);
	ret = -EBUSY;
	}
	return ret;
	}

	static int
	nfnl_acct_del(struct sock nfnl, struct sk_buff skb,
	const struct nlmsghdr nlh, const struct nlattr const tb[])
	{
	char *acct_name;
	struct nf_acct *cur;
	int ret = -ENOENT;

	if (!tb[NFACCT_NAME]) {
	list_for_each_entry(cur, &nfnl_acct_list, head)
	nfnl_acct_try_del(cur);

	return 0;
	}
	acct_name = nla_data(tb[NFACCT_NAME]);

	list_for_each_entry(cur, &nfnl_acct_list, head) {
	if (strncmp(cur->name, acct_name, NFACCT_NAME_MAX) != 0)
	continue;

	ret = nfnl_acct_try_del(cur);
	if (ret < 0)
	return ret;

	break;
	}
	return ret;
	}

	static const struct nla_policy nfnl_acct_policy[NFACCT_MAX+1] = {
	[NFACCT_NAME] = { .type = NLA_NUL_STRING, .len = NFACCT_NAME_MAX-1 },
	[NFACCT_BYTES] = { .type = NLA_U64 },
	[NFACCT_PKTS] = { .type = NLA_U64 },
	};

	static const struct nfnl_callback nfnl_acct_cb[NFNL_MSG_ACCT_MAX] = {
	[NFNL_MSG_ACCT_NEW] = { .call = nfnl_acct_new,
	.attr_count = NFACCT_MAX,
	.policy = nfnl_acct_policy },
	[NFNL_MSG_ACCT_GET] = { .call = nfnl_acct_get,
	.attr_count = NFACCT_MAX,
	.policy = nfnl_acct_policy },
	[NFNL_MSG_ACCT_GET_CTRZERO] = { .call = nfnl_acct_get,
	.attr_count = NFACCT_MAX,
	.policy = nfnl_acct_policy },
	[NFNL_MSG_ACCT_DEL] = { .call = nfnl_acct_del,
	.attr_count = NFACCT_MAX,
	.policy = nfnl_acct_policy },
	};

	static const struct nfnetlink_subsystem nfnl_acct_subsys = {
	.name = "acct",
	.subsys_id = NFNL_SUBSYS_ACCT,
	.cb_count = NFNL_MSG_ACCT_MAX,
	.cb = nfnl_acct_cb,
	};

	MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_ACCT);

	struct nf_acct nfnl_acct_find_get(const char acct_name)
	{
	struct nf_acct cur, acct = NULL;

	rcu_read_lock();
	list_for_each_entry_rcu(cur, &nfnl_acct_list, head) {
	if (strncmp(cur->name, acct_name, NFACCT_NAME_MAX)!= 0)
	continue;

	if (!try_module_get(THIS_MODULE))
	goto err;

	if (!atomic_inc_not_zero(&cur->refcnt)) {
	module_put(THIS_MODULE);
	goto err;
	}

	acct = cur;
	break;
	}
	err:
	rcu_read_unlock();
	return acct;
	}
	EXPORT_SYMBOL_GPL(nfnl_acct_find_get);

	void nfnl_acct_put(struct nf_acct *acct)
	{
	atomic_dec(&acct->refcnt);
	module_put(THIS_MODULE);
	}
	EXPORT_SYMBOL_GPL(nfnl_acct_put);

	void nfnl_acct_update(const struct sk_buff skb, struct nf_acct nfacct)
	{
	atomic64_inc(&nfacct->pkts);
	atomic64_add(skb->len, &nfacct->bytes);
	}
	EXPORT_SYMBOL_GPL(nfnl_acct_update);

	static int __init nfnl_acct_init(void)
	{
	int ret;

	pr_info("nfnl_acct: registering with nfnetlink.\n");
	ret = nfnetlink_subsys_register(&nfnl_acct_subsys);
	if (ret < 0) {
	pr_err("nfnl_acct_init: cannot register with nfnetlink.\n");
	goto err_out;
	}
	return 0;
	err_out:
	return ret;
	}

	static void __exit nfnl_acct_exit(void)
	{
	struct nf_acct cur, tmp;

	pr_info("nfnl_acct: unregistering from nfnetlink.\n");
	nfnetlink_subsys_unregister(&nfnl_acct_subsys);

	list_for_each_entry_safe(cur, tmp, &nfnl_acct_list, head) {
	list_del_rcu(&cur->head);
	/* We are sure that our objects have no clients at this point,
	* it's safe to release them all without checking refcnt. */
	kfree_rcu(cur, rcu_head);
	}
	}

	module_init(nfnl_acct_init);
	module_exit(nfnl_acct_exit);